fixed System.InvalidOperationException: 'The hyperlink for cell A1 references relation rId1, but that didn't exist!'

[htoyama]

NPOI Version

2.7.0

File Type

• XLSX
• XLS
• DOCX
• XLSM
• OTHER

Upload the Excel File

Book1.xlsx

Reproduce Steps

workbook.CloneSheet("Sheet1");

Issue Description

System.InvalidOperationException: 'The hyperlink for cell A1 references relation rId1, but that didn't exist!'
RelationshipのIdは、コピー元のワークシートと同じにしないと例外になる。

diff --git a/ooxml/XSSF/UserModel/XSSFWorkbook.cs b/ooxml/XSSF/UserModel/XSSFWorkbook.cs
index 2940dc72..da0981aa 100644
--- a/ooxml/XSSF/UserModel/XSSFWorkbook.cs
+++ b/ooxml/XSSF/UserModel/XSSFWorkbook.cs
@@ -626,7 +626,7 @@ public ISheet CloneSheet(int sheetNum, String newName)
                     if (pr.TargetMode == TargetMode.External)
                     {
                         clonedSheet.GetPackagePart().AddExternalRelationship
-                            (pr.TargetUri.OriginalString, pr.RelationshipType, null);
+                            (pr.TargetUri.OriginalString, pr.RelationshipType, pr.Id);
                     }
                 }
             }

[tonyqus]

Can you create a PR?